Purified hydrogen is used in the manufacture of many products including metals, edible fats and oils, and semiconductors and microelectronics. Purified hydrogen is also an important fuel source for many energy conversion devices, such as fuel-cell systems, and especially proton-exchange-membrane fuel-cell (PEMFC) systems. For example, fuel cells use purified hydrogen and an oxidant to produce an electrical potential. By chemical reaction, a process known as steam reforming produces hydrogen and certain byproducts or impurities. A subsequent purification process removes the undesirable impurities to provide hydrogen sufficiently purified for application to a fuel cell. Examples of fuel-cell systems are disclosed in U.S. Pat. No. 5,861,137, and U.S. patent application Ser. Nos. 08/951,091 and 09/190,917, the disclosures of which are hereby incorporated by reference.
The invention includes a hydrogen-permeable metal membrane with increased hydrogen flux compared to conventional hydrogen-permeable metal membranes. Without sacrificing selectivity or purity, the membrane enables a greater hydrogen throughput. A method for preparing the membrane includes at least one etching step in which a volume of etchant is used to selectively remove material from the membrane's surface. Methods for detecting and repairing holes or other defects in the membrane are also disclosed.
Many other features of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying drawings in which preferred embodiments incorporating the principles of this invention are disclosed as illustrative examples only.